Fiber-reinforced resin, process for producing same, and molded article

ABSTRACT

(A) A reinforcing fiber, (B) a resin particle, and (C) a matrix resin are combined to prepare a resin composition which improves a reinforcing effect by the reinforcing fiber. The reinforcing fiber (A) contains a carbon fiber. The resin particle (B) contains a semicrystalline thermoplastic resin, the semicrystalline thermoplastic resin in the resin particle (B) has an exothermic peak in a temperature range between a glass transition temperature of the semicrystalline thermoplastic resin and a melting point of the semicrystalline thermoplastic resin, the peak being determined by heating the resin particle (B) at a rate of 10° C./min. by differential scanning calorimetry (DSC), and the resin particle (B) has an average particle size of 3 to 40 μm. The semicrystalline thermoplastic resin may be a polyamide resin having a melting point of not lower than 150° C. (particularly, a polyamide resin having an alicyclic structure and a glass transition temperature of not lower than 100° C., or a polyamide resin having a γ-type crystal structure or a degree of crystallinity of not more than 50%). The matrix resin (C) may be a thermosetting resin.

TECHNICAL FIELD

The present invention relates to resin compositions containingreinforcing fibers, processes for producing the same, and moldedarticles (or fiber-reinforced composites) containing the resincompositions.

BACKGROUND ART

Carbon-fiber-reinforced plastics (CFRPs), which contains carbon fibersand matrix resins, have excellent strength, stiffness, or othercharacteristics and are used for various applications, for example,primary structure members of flying machines, automotive members,windmill blades, and chassis for various electronic machines. For suchapplications, particularly important physical properties mainly includephysical strength, for example, impact strength, elastic modulus,flexural strength, and interlaminar toughness. In order to improve suchphysical properties, it is being devised to add a variety of fillers toa CFRP containing a matrix resin (for example, an epoxy resin component)and a carbon fiber. In particular, reinforcement of CFRP using polyamidefine particles is now being investigated variously.

Japanese Patent Application Laid-Open Publication No. 2014-145003(JP-2014-145003A, Patent Document 1) discloses a pre-preg (anintermediate material for molding) containing a reinforcing fiber, anepoxy resin, and two kinds of polymer particles with different averageparticle sizes; of the polymer particles, a larger polymer particlehaving an average particle size of 10 to 30 μm has a glass transitiontemperature of 80 to 180° C. In working examples of this document, apolyamide fine particle is prepared by chemical pulverization in which apolyamide is dissolved in a solvent and then a poor solvent is added tothe resulting solution to give a precipitate.

Japanese Patent No. 5655976 (JP-5655976B, Patent Document 2) discloses apre-preg which consists of a composition containing a reinforcing fiber,a thermosetting resin, a crystalline polyamide, and an amorphouspolyamide, wherein the composition contains a particle having a specificdynamic storage modulus and a glass transition temperature of 80 to 180°C. In working examples of this document, a polyamide fine particle isprepared by chemical pulverization in which a crystalline polyamide andan amorphous polyamide are dissolved in a solvent and then a poorsolvent is added to the resulting solution to give a precipitate.

WO2015/033998 pamphlet (Patent Document 3) discloses, as a compositionfor a fiber-reinforced composite utilizable as a pre-preg, a compositioncontaining a reinforcing fiber, a globular polyamide resin particlehaving an average particle size of 12 to 70 μm, and a matrix resin. Inworking examples of this document, a polyamide resin particle isprepared by forced emulsification in which a polyamide is melt-kneadedusing a material incompatible with the polyamide.

Unfortunately, these polyamide particles fail to sufficiently improve areinforcing effect by the reinforcing fiber. Further, the polyamideparticles described in Patent Document 2, which contain two kinds ofpolyamide particles, need homogeneous mixing, and this results indifficult handling.

CITATION LIST Patent Literature

Patent Document 1: JP-2014-145003A (claim 1 and Examples)

Patent Document 2: JP-5655976B (Claims and Examples)

Patent Document 3: WO2015/033998 pamphlet (Claims and Examples)

SUMMARY OF INVENTION Technical Problem

It is therefore an object of the present invention to provide a resincomposition in which a reinforcing effect by a reinforcing fiber (inparticular, a carbon fiber) is improved, a process for producing theresin composition, and a molded article containing the resincomposition.

Another object of the present invention is to provide a resincomposition which is easy to handle and easily improves an interlaminartoughness of a CFRP, a process for producing the resin composition, anda molded article containing the resin composition.

Solution to Problem

The inventors of the present invention focused attention on thermalcharacteristics of resin fine particles to achieve the above objects.Specifically, in a production process of a CFRP, although a fineparticle added is exposed under an environment of a temperature beyond150° C. over a long period of time by a curing reaction of an epoxyresin and is chemically influenced by the epoxy resin or a curing agentduring the curing reaction, a polyamide fine particle itself to be usedfor reinforcing the CFRP has been hardly examined for the thermalcharacteristics. For example, in each of Patent Documents 1 and 2, thepolyamide resin is examined for the glass transition temperature or thetemperature dependency of dynamic storage modulus G′. However, thesecharacteristics are characteristics of the polyamide resin itselfconstituting fine particle and not those of the fine particle. Inparticular, for a semicrystalline resin such as the polyamide resinconstituting the fine particle, when the resin is cooled and solidifiedafter melting by heat, the molecular higher-order structure (e.g.,degree of crystallinity) after the solidification significantly variesdepending on the thermal hysteresis (in particular, heating by drying)of the resin after the solidification. Although such a difference inhigher-order structure greatly affects a reinforcing effect by the resinfine particle in the CFRP, these respects have not been examined in theconventional art. For example, Patent Document 3 fails to describe aheat treatment to the obtained polyamide resin fine particle. A personwith ordinary skill in the art usually heats the polyamide resin fineparticle at a temperature as high as possible to improve the productionefficiency, that is, at a temperature not lower than the glasstransition temperature of the polymer, in drying for removing a solvent.Accordingly, it has been found that the resin particle produced byforced emulsification in Patent Document 3 is crystallized by heatingfor drying and has an insufficient reinforcing effect on the CFRP.

For reinforcement, a fine particle may be added to a thermoplastic resinor other resins, without limitation to the CFRP. The reason for theaddition is that an extension energy of cracks generated in the matrixdue to impact or other causes is absorbed by an energy for destroyingthe interface between the fine particle and the matrix or an energy fordeforming or destroying the fine particle. Thus, usually there ispreferably a sufficient affinity between the fine particle to be addedand the matrix resin. On the contrary, there is preferably no gap orothers therebetween. Moreover, the destructive mode of the fine particleitself is preferably not brittle but ductile. These tendencies each arestrongly related to the higher-order structure (e.g., degree ofcrystallinity) of the fine particle itself. However, at present, such anexamination has not been made.

In these circumstances, the inventors of the present invention madeintensive studies to achieve the above objects and finally found thefollowing: as a resin particle to be added to a composition containing amatrix resin and a reinforcing fiber, use of a fine particle having alow degree of crystallinity so that a crystallization peak may beobserved in a first heating (1st Heat) process of a differentialscanning calorimetric analysis (DSC) effectively improves a reinforcingeffect by the reinforcing fiber (particularly, a carbon fiber). Thepresent invention was accomplished based on the above findings.

Representative examples of the method for producing the resin particlemay include (1) a cryogenic pulverization (for example, a method thatcomprises cooling and embrittling a resin with liquid nitrogen or othermeans and then pulverizing or crushing the resin by a physical force togive a particle (or a powder)), (2) a chemical pulverization (forexample, a method that comprises dissolving a resin in a solvent andthen adding the resulting solution to a poor solvent for precipitation),(3) a polymerization (for example, a method that comprises polymerizinga raw material by suspension polymerization or emulsion polymerizationto give a particle), (4) a forced emulsification {for example, a methodthat comprises melt-kneading a resin and a material incompatible withthe resin [e.g., a water-soluble material, such as a water-solublepolymer (such as a poly(ethylene glycol)) or a saccharide (such as apolysaccharide or an oligosaccharide)] to give a dispersion containing aresin particle dispersed in the incompatible material (water-solublepolymer) and then removing the incompatible material from thedispersion}, and (5) a laser method (a method that comprisesinstantaneously melting a fibrous resin by laser and flying the resin ina decompression bath or others to give a resin particle). The inventorsof the present invention also found that a specific fine particle havinga low crystallinity is produced by preparing a particle using the forcedemulsification selected from these methods and adjusting a thermalhistory (in particular, a drying condition) of the resulting particle toa specified condition.

Further, regarding the resin constituting the fine particle, anamorphous resin fine particle naturally has a lower degree ofcrystallinity than that of a semicrystalline resin fine particle. Anamorphous resin that can maintain a shape thereof at 150 to 190° C.being a curing condition of an epoxy resin has an extremely high glasstransition temperature and is brittle in a temperature range from a roomtemperature to about 100° C. Thus, the amorphous resin fails to achievea sufficient reinforcing effect. Accordingly, the inventors of thepresent invention found that it is necessary that a resin capable ofimproving a reinforcing effect be a semicrystalline resin and be a resinhaving a low degree of crystallinity as a fine particle.

That is, an aspect of the present invention provides a resin compositioncomprising (A) a reinforcing fiber, (B) a resin particle, and (C) amatrix resin; the reinforcing fiber (A) contains a carbon fiber, theresin particle (B) contains a semicrystalline thermoplastic resin, thesemicrystalline thermoplastic resin in the resin particle (B) (the resinparticle (B)) has an exothermic peak in a temperature range between aglass transition temperature of the semicrystalline thermoplastic resin(the resin particle (B)) and a melting point of the semicrystallinethermoplastic resin (the resin particle (B), the exothermic peak beingdetermined by heating the resin particle (B) at a rate of 10° C./min. bydifferential scanning calorimetry (DSC), and the resin particle (B) hasan average particle size of 3 to 40 μm.

The semicrystalline thermoplastic resin may be a polyamide resin havinga melting point of not lower than 150° C. (in particular, a polyamideresin having an alicyclic structure and a glass transition temperatureof not lower than 100° C., or an aliphatic polyamide resin having aγ-type crystal structure). The semicrystalline thermoplastic resin maybe a polyamide resin having a γ-type crystal structure or a degree ofcrystallinity of not more than 50% (in particular, an aliphaticpolyamide resin). The resin particle (B) may further contain an impactmodifier. The matrix resin (C) may be a thermosetting resin. The resinparticle (B) may have a spherical shape and an average particle size of15 to 25 μm.

Another aspect of the present invention provides a process for producingthe resin composition; the process comprises a resin particle productionstep which comprises melt-kneading a semicrystalline thermoplastic resinand an aqueous medium incompatible with the resin to a melt-kneadedproduct and removing the aqueous medium from the melt-kneaded productwith a hydrophilic solvent to give (B) a resin particle, and animpregnation step for impregnating (A) a reinforcing fiber with theresulting resin particle (B) and (C) a matrix resin. In the resinparticle production step, after the aqueous medium is removed, theresulting product may be dried at a temperature of not higher than(Tg+40)° C., wherein Tg represents a glass transition temperature of thesemicrystalline thermoplastic resin.

Still another aspect of the present invention provides a molded articlecontaining the resin composition.

Still another aspect of the present invention provides an additive for acomposition comprising (A) a reinforcing fiber containing a carbon fiberand (C) a matrix resin to increase or improve a reinforcing effect ofthe reinforcing fiber (A); the additive contains (B) a resin particle,the resin particle (B) contains a semicrystalline thermoplastic resin,the semicrystalline thermoplastic resin in the resin particle (B) has anexothermic peak in a temperature range between a glass transitiontemperature of the semicrystalline thermoplastic resin and a meltingpoint of the semicrystalline thermoplastic resin (the resin particle(B), the exothermic peak being determined by heating the resin particle(B) at a rate of 10° C./min. by differential scanning calorimetry (DSC),and the resin particle (B) has an average particle size of 3 to 40 μm.

Advantageous Effects of Invention

According to the present invention, combination of a resin particlehaving a specific degree of crystallinity with a carbon fiber and amatrix resin improves a reinforcing effect by a reinforcing fiber (inparticular, a carbon fiber). In particular, a resin composition, aprocess producing the resin composition, and a molded article containingthe resin composition are provided. In particular, simple impregnationof a resin particle having thermal characteristics measured andcontrolled using DSC and a matrix resin with a reinforcing fiber easilyimproves the interlaminar toughness of a CFRP and allows easy handling.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a curve showing heat absorption in raising the temperature ofan alicyclic polyamide particle obtained in Example 1 at a rate of 10°C./min. by a differential scanning calorimeter (DSC).

FIG. 2 is a curve showing heat absorption in raising the temperature ofan alicyclic polyamide particle obtained in Comparative Example 1 at arate of 10° C./min. by a DSC.

FIG. 3 is a wide-angle X-ray diffraction chart of alicyclic polyamideparticles obtained in Example 1 and Comparative Example 1.

FIG. 4 is a curve showing heat absorption in raising the temperature ofa polyamide 12 particle obtained in Example 2 at a rate of 10° C./min.by a DSC.

FIG. 5 is a wide-angle X-ray diffraction chart of a polyamide 12particle obtained in Example 2.

FIG. 6 is a curve showing heat absorption in raising the temperature ofa polyamide 12 particle obtained in Comparative Example 3 at a rate of10° C./min. by a DSC.

FIG. 7 is a wide-angle X-ray diffraction chart of a polyamide 12particle obtained in Comparative Example 3.

FIG. 8 is a wide-angle X-ray diffraction chart of a polyamide 1010particle obtained in Example 3.

FIG. 9 is a wide-angle X-ray diffraction chart of a polyamide 1010particle obtained in Comparative Example 4.

DESCRIPTION OF EMBODIMENTS

[Resin Composition]

The resin composition of the present invention comprises (A) areinforcing fiber, (B) a resin particle, and (C) a matrix resin (amatrix-forming resin). The resin composition, which can be used as acomposition for obtaining a fiber-reinforced composite (or afiber-reinforced resin) as described later, may also be referred to as acomposition for a fiber-reinforced composite (or a composition for afiber-reinforced resin).

(A) Reinforcing Fiber

The reinforcing fiber (strengthening fiber, fibrous reinforcingmaterial, fibrous filler, fibrous filling material) (A) is a componentthat reinforces (or strengthens) a matrix resin and contains a carbonfiber. The carbon fiber may include, but should not be limited to, apitch-based fiber, a polyacrylonitrile (PAN)-based carbon fiber, orother fibers. These carbon fibers may be used alone or in combination.

The reinforcing fiber (A) may further contain a non-carbon fiber inaddition to the carbon fiber. The non-carbon fiber may include aninorganic fiber (for example, a glass fiber, a boron fiber, analuminosilicate fiber, an aluminum oxide fiber, a silicon carbide fiber,a metal fiber, and a potassium titanate fiber), an organic fiber {forexample, a polyester fiber [e.g., an aromatic polyester fiber (e.g., apoly(alkylene arylate) fiber such as a poly(ethylene terephthalate)fiber)], a polyamide fiber [e.g., an aromatic polyamide fiber (e.g., anaramid fiber)], and a regenerated fiber (e.g., a rayon)}. Thesenon-carbon fibers may be used alone or in combination.

For a combination of the carbon fiber and the non-carbon fiber (forexample, a glass fiber, an organic fiber), the proportion of the carbonfiber in the whole reinforcing fiber may be, for example, not less than30% by volume, preferably not less than 50% by volume, and morepreferably not less than 70% by volume (in particular, not less than 90%by volume) or may be 100% by volume (the carbon fiber alone).

The reinforcing fiber (A) may be surface-treated.

The reinforcing fiber (A) may have an average diameter selected,depending on the species thereof, from a range of about 0.5 to 1000 μm(e.g., about 1 to 500 μm). For example, the reinforcing fiber may havean average diameter of about 1 to 300 μm (e.g., about 2 to 100 μm),preferably about 3 to 70 μm, more preferably about 5 to 50 μm (e.g.,about 5 to 30 μm).

In particular, the carbon fiber may have an average diameter (averagefiber diameter) of, for example, about 1 to 100 μm (e.g., about 1.5 to70 μm), preferably about 2 to 50 μm (e.g., about 2.5 to 40 μm), morepreferably about 3 to 30 μm, particularly about 5 to 20 μm (e.g., about6 to 15 μm), and usually about 5 to 15 μm (e.g., about 7 to 10 μm).

In the present invention, the fiber diameter can be measured by a commonmethod. For example, the fiber diameter can be determined by measuringfiber diameters of 10 or more fibers with an electron microscope andcalculating the average of the measured values.

The reinforcing fiber (A) may be either a short fiber or a long fiber.In particular, the reinforcing fiber may be a long fiber. The long fibermay be either a continuous fiber or a discontinuous fiber or may becombination of a continuous fiber and a discontinuous fiber.

The reinforcing fiber (A) may be used to form a fabric (or a cloth or atextile). The fabric (fiber assembly) may include, for example, a wovenfabric (a woven product), a nonwoven fabric, and a knit fabric (a knitproduct). The reinforcing fibers (A) may be contained in thecomposition, which comprises the resin particle (B) and the matrix resin(C), in an embodiment that the reinforcing fibers are arranged in thesame direction (or one direction) as described later.

The structure of the cloth can suitably be selected according to thespecies of the cloth. For example, the structure of the woven fabric(woven construction) may include, but should not be limited to, a plainweave, a twill weave, a satin weave, or other structures. The structureof the knit fabric (knit construction) may include a warp knit (forexample, a tricot), a weft knit (for example, a plain stitch and a Tuckstitch), or other structures.

(B) Resin Particle (Semicrystalline Thermoplastic Resin Particle)

The resin component constituting the resin particle (B) comprises asemicrystalline thermoplastic resin. The semicrystalline thermoplasticresin is not limited to a particular resin and is any resin that canimprove (or assist) the reinforcing effect by the reinforcing fiber. Forexample, the thermoplastic resin may include a polyamide resin, apolyester resin [for example, an aromatic polyester resin such as apoly(ethylene terephthalate)], a polyacetal resin, a polysulfide resin,a polysulfone resin (including a polyethersulfone resin), apolyetherketone resin, and a polyolefin resin. These semicrystallinethermoplastic resins may be used alone or in combination.

Among them, in combination with an epoxy resin as the matrix resin, thepolyamide resin is preferred considering effective and easy exertion ofthe reinforcing effect. For example, the polyamide resin may include analiphatic polyamide resin, an alicyclic polyamide resin, and an aromaticpolyamide resin. The polyamide resin may be a homopolyamide or acopolyamide. The polyamide resin may have any terminal group withoutlimitation. The terminal group may be an amino group, a carboxyl group,or an acid anhydride group.

Among the aliphatic polyamide resins, the homopolyamide may include ahomo- or co-polyamide of an aliphatic diamine component and an aliphaticdicarboxylic acid component, a homo- or co-polyamide of a lactam or anaminocarboxylic acid, and a copolyamide of a first amide-formingcomponent of an aliphatic diamine component and an aliphaticdicarboxylic acid component and a second amide-forming component of alactam or an aminocarboxylic acid. Examples of the aliphatic diaminecomponent may include an alkanediamine, for example, a C₄₋₁₆alkylenediamine such as tetramethylenediamine, hexamethylenediamine, ordodecanediamine, preferably a C₆₋₁₄ alkylenediamine, and more preferablya C₆₋₁₂ alkylenediamine. Examples of the aliphatic dicarboxylic acidcomponent may include an alkanedicarboxylic acid, for example, aC₄₋₂₀alkanedicarboxylic acid such as adipic acid, sebacic acid, ordodecanedioic acid, preferably a C₅₋₁₈ alkanedicarboxylic acid, and morepreferably a C₆₋₁₆ alkanedicarboxylic acid. Examples of the lactam mayinclude, for example, a lactam having about 4 to 20 (preferably about 4to 16) carbon atoms, such as s-caprolactam or ω-laurolactam. Examples ofthe aminocarboxylic acid may include, for example, aC₄₋₂₀aminocarboxylic acid such as ω-aminoundecanoic acid, preferably aC₄₋₁₆aminocarboxylic acid, and more preferably a C₆₋₁₄aminocarboxylicacid.

Concrete examples of the aliphatic polyamide resin may include apolyamide 6, a polyamide 11, a polyamide 12, a polyamide 46, a polyamide66, a polyamide 610, a polyamide 611, a polyamide 612, a polyamide 613,a polyamide 1010, a polyamide 1012, a polyamide 66/11, a polyamide66/12, a polyamide 6/12/612, or others.

The alicyclic polyamide resin may include, for example, a homopolyamideor copolyamide containing as a constituent at least one member selectedfrom the group consisting of an alicyclic diamine component and analicyclic dicarboxylic acid component. For example, as the alicyclicpolyamide resin, there may be used an alicyclic polyamide which containsan alicyclic diamine and/or an alicyclic dicarboxylic acid as at leastone of diamine components and dicarboxylic acid components. Inparticular, as the diamine component and the dicarboxylic acidcomponent, combination use of the above-exemplified aliphatic diaminecomponent and/or aliphatic dicarboxylic acid component with thealicyclic diamine component and/or alicyclic dicarboxylic acid componentis preferred. Such an alicyclic polyamide resin, which has a hightransparency, is known as what is called a transparent polyamide.

The alicyclic diamine component may include a diaminocycloalkane such asdiaminocyclohexane (e.g., a diaminoC₅₋₁₀cycloalkane); and abis(aminocycloalkyl)alkane such as bis(4-aminocyclohexyl)methane,bis(4-amino-3-methylcyclohexyl)methane, or2,2-bis(4′-aminocyclohexyl)propane [e.g., abis(aminoC₅₋₈cycloalkyl)C₁₋₃alkane]; a hydrogenated xylylenediamine; orother components. The alicyclic diamine component may have a substituentsuch as an alkyl group (a C₁₋₆alkyl group such as methyl group or ethylgroup, preferably a C₁₋₄alkyl group, and more preferably a C₁₋₂alkylgroup). The alicyclic dicarboxylic acid may include acycloalkanedicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid or1,3-cyclohexanedicarboxylic acid (e.g., a C₅₋₁₀cycloalkane-dicarboxylicacid), or other compounds.

Representative examples of the alicyclic polyamide resin may include acondensation product of an alicyclic diamine component [e.g., abis(aminocyclohexyl)alkane] and an aliphatic dicarboxylic acid component[e.g., an alkanedicarboxylic acid (e.g., a C₄₋₂₀alkane-dicarboxylic acidcomponent)].

The aromatic polyamide resin may include a polyamide in which at leastone of an aliphatic diamine component and an aliphatic dicarboxylic acidcomponent in an aliphatic polyamide resin is an aromatic component, forexample, a polyamide in which a diamine component is an aromatic diaminecomponent [for example, a condensation product (e.g., MXD-6) of anaromatic diamine (e.g., m-xylylenediamine) and an aliphatic dicarboxylicacid], and a polyamide in which a dicarboxylic acid component is anaromatic component [for example, a condensation product of an aliphaticdiamine (e.g., trimethylhexamethylenediamine) and an aromaticdicarboxylic acid (such as terephthalic acid or isophthalic acid)]. Thearomatic polyamide resin may be a fully aromatic polyamide (aramid) inwhich a diamine component and a dicarboxylic acid component are aromaticcomponents [e.g., a poly(m-phenyleneisophthalamide)].

These semicrystalline polyamide resins may be used alone or incombination. Among these resins, considering a more reinforcing effecton the matrix resin, a semicrystalline polyamide (a polyamide having acrystallinity) such as an alicyclic polyamide or an aliphatic polyamide(an alicyclic polyamide and/or an aliphatic polyamide) is preferred. Inthe respect that the resin particle (B) is easy to richly distribute onor near the reinforcing fiber (A), the alicyclic polyamide resin (apolyamide resin having an alicyclic structure) is particularlypreferred.

The semicrystalline thermoplastic resin (in particular, thesemicrystallinepolyamide resin) may have a number average molecularweight of, for example, about 8000 to 200000, preferably about 9000 to150000, and more preferably about 10000 to 100000. The number averagemolecular weight can be measured by gel permeation chromatography usinga polystyrene or other substances as a standard substance, or othermeans.

The melting point of the semicrystalline thermoplastic resin (inparticular, the semicrystalline polyamide resin) is not limited to aparticular temperature. A polyamide resin having a relatively highmelting point may preferably be used. Such a semicrystalline polyamideresin tends to maintain a spherical shape thereof at a high level inproducing a composition or a molded article, and this probablycontributes to efficiently obtaining the reinforcing effect by thereinforcing fiber (A). Such a semicrystalline polyamide resin (such asan aliphatic polyamide resin or an alicyclic polyamide resin) may have amelting point of, for example, not lower than 150° C. (e.g., about 155to 350° C., preferably not lower than 160° C. (e.g., about 165 to 300°C.), and more preferably not lower than 170° C. (e.g., about 175 to 270°C.). The semicrystalline polyamide resin may have a melting point (orsoftening point) not lower than (or higher than) a molding temperatureof the composition [for example, a curing temperature of a curable resin(e.g., an epoxy resin) as the matrix resin]. A semicrystalline polyamideresin having an excessively high melting point may fail to improve thereinforcing effect by the reinforcing fiber (A).

The semicrystalline thermoplastic resin (in particular, thesemicrystalline polyamide resin) may have a glass transition temperatureof, for example, not lower than 30° C. (for example, about 40 to 200°C.). In particular, the alicyclic polyamide resin may have a glasstransition temperature of not lower than 100° C. (for example, about 105to 200° C.), preferably not lower than 110° C. (for example, about 115to 180° C.), and more preferably not lower than 120° C. (for example,about 125 to 150° C.); the aliphatic polyamide resin may have a glasstransition temperature of not lower than 30° C. (for example, about 30to 150° C.), preferably not lower than 40° C. (for example, about 40 to120° C.), and more preferably not lower than 45° C. (for example, about45 to 100° C.). A semicrystalline polyamide resin having an excessivelyhigh glass transition temperature may fail to improve the reinforcingeffect by the reinforcing fiber (A).

The degree of crystallinity of the semicrystalline thermoplastic resin(in particular, the semicrystalline polyamide resin) can be selectedaccording to the species of the resin, and may be not more than 80% (forexample, 75 to 1%) and preferably not more than 50% (for example, 50 to10%). In a case where the semicrystalline thermoplastic resin is analicyclic polyamide resin, the alicyclic polyamide resin may have adegree of crystallinity of not more than 40%, and has a degree ofcrystallinity of, for example, about 30 to 1%, preferably about 20 to1%, and more preferably about 20 to 5%. A semicrystalline aliphaticpolyamide having a C₆₋₁₀alkane unit, such as a polyamide 1010, may havea degree of crystallinity of not more than 50%, and has a degree ofcrystallinity of, for example, about 50 to 1%, preferably about 45 to10%, and more preferably about 43 to 30%. A semicrystalline aliphaticpolyamide having a C₁₁₋₁₃alkane unit, such as a polyamide 12, may have adegree of crystallinity of not more than 80%, and has a degree ofcrystallinity of, for example, about 80 to 10%, preferably about 78 to30%, and more preferably about 75 to 35%. A semicrystalline polyamideresin having an excessively high degree of crystallinity may fail toimprove the reinforcing effect by the reinforcing fiber (A). Accordingto the present invention, the degree of crystallinity can be measured bya conventional method, for example, X-ray diffraction, differentialscanning calorimetry (DSC), particularly can be measured based onwide-angle X-ray diffraction (WAXD) as described in Examples mentionedbelow.

The resin particle (B) (the semicrystalline thermoplastic resin in theresin particle (B)) has an exothermic peak in a temperature rangebetween the glass transition temperature of the resin particle (B) (thesemicrystalline thermoplastic resin) and the melting point of the resinparticle (B) (the semicrystalline thermoplastic resin) when the resinparticle (B) is heated at a rate of 10° C./min. by differential scanningcalorimetry (DSC). The exothermic peak is within the above-mentionedtemperature range, and, for example, may be positioned at a temperature1 to 70° C. higher than the glass transition temperature, or may bepositioned at a temperature preferably about 1 to 60° C., morepreferably about 1 to 50° C. (particularly about 1 to 40° C.) higherthan the glass transition temperature. According to the presentinvention, probably because the resin particle (B) having such thermalcharacteristics (crystal structure) easily acts on the matrix resin (C)(in particular, a thermosetting resin such as an epoxy resin), thereinforcing effect by the reinforcing fiber (A) is improvable.

The crystal structure of the semicrystalline thermoplastic resinconstituting the resin particle (B) is not particularly limited to aspecific one. For example, the crystal structure of the semicrystallinepolyamide resin may be any crystal structure of α-type, γ-type, andα+γ-type. Among them, the semicrystalline aliphatic polyamide resin (inparticular, a semicrystalline aliphatic polyamide having a C₁₁₋₁₃alkaneunit, such as a polyamide 12) preferably has a γ-type crystal structure.In the present description and claims, the crystal structure of thesemicrystalline polyamide resin can be determined based on the presenceor absence of peak(s) in a diffraction angle 20 range of 15 to 30° in awide-angle X-ray diffraction chart, as follows.

Amorphous structure or low-crystal structure: gentle mountain shapehaving no peak

α-Type crystal structure: sharp mountain shape having two peaks

γ-Type crystal structure: sharp mountain shape having one peak (forexample, mountain shape having one peak at 2θ of 21.5°±0.2°)

α+γ-Type crystal structure: sharp mountain shape having three peakscomposed of 2θ of α-type two peaks and γ-type one peak existing betweenthe α-type two peaks

The resin particle (B) preferably has a spherical shape. The sphericalshape may include a highly spherical shape or a substantially sphericalshape [for example, a shape having a smooth surface (or having no unevenstructure on a surface thereof) and having a major axis slightly longerthan a minor axis (for example, a ratio of major axis/minor axis ofabout 1.3/1 to 1/1, preferably about 1.2/1 to 1/1, and more preferablyabout 1.1/1 to 1/1)]. In particular, the highly spherical shape ispreferred. Moreover, since at the higher sphericity the specific surfacearea becomes smaller, the specific surface area may be used as an indexof the sphericity (spherical shape) in the present description andclaims. For example, in a case where the resin particle (B) has anaverage particle size of 20 μm, the resin particle (B) may have a BETspecific surface area of, for example, not more than 1 m²/g, preferablynot more than 0.5 m²/g, and more preferably not more than 0.4 m²/g.Incidentally, a resin particle having a specific gravity of 1.0 and anaverage particle size of 20 μm has a theoretical minimum specificsurface area of 0.15 m²/g.

As the shape of the resin particle, an amorphous shape, a potato shape,a spherical shape, or other shapes are known. Such a shape ispractically determined according to a method for producing the particle.

The resin particle (B) may have an average particle size (an averageparticle diameter) from a range of not less than 3 μm (for example, 3 to85 μm). For example, the average particle size may be about 3 to 40 μm,preferably about 5 to 35 μm, and more preferably about 10 to 30 μm(particularly about 15 to 25 μm). A resin particle (B) having anextremely small average particle size may fail to improve thereinforcing effect by the reinforcing fiber (A). In the presentinvention, the average particle size is expressed as a number averageprimary particle size and can be measured by laser diffractionscattering method or other means.

The above range is a range of the average particle size, although,probably, a resin particle having a particle size within the above rangeof the average particle size mainly contributes to an efficientreinforcing effect. Accordingly, the resin particle (B) may comprise aresin particle having a particle size within the range of 3 to 40 μm(particularly 15 to 25 μm) at a proportion of not less than 50% (e.g.,not less than 60%), preferably not less than 70%, more preferably notless than 80%, and particularly not less than 90% in the whole resinparticle (B) on the basis of the number of particles.

The average particle size of the resin particle (B) can be selectedaccording to the average diameter of the reinforcing fiber (A). Forexample, the average particle size of the resin particle (B) may beabout 0.5 to 15 times (e.g., about 0.7 to 12 times), preferably about 1to 10 times (e.g., about 1.5 to 5 times), and more preferably about 2 to4 times (e.g., about 2.5 to 3.5 times) as large as the average diameter(average fiber diameter) of the reinforcing fiber (A) or may usually beabout 1.5 to 15 times (e.g., about 2 to 10 times) as large as theaverage diameter (average fiber diameter) of the reinforcing fiber (A).A resin particle (B) having such a particle size tends to be richlydistributed on or near (or around) the reinforcing fiber, easilyachieving an efficiently increased reinforcing effect by the reinforcingfiber (A).

The resin particle (B) contains the semicrystalline thermoplastic resin,and may further contain an impact modifier. The impact modifier mayinclude, for example, a polyolefin resin modified with an acid (anacid-modified polyolefin resin) and a resin having anepoxy-group-containing group such as glycidyl group. These impactmodifiers may be used alone or in combination. Among these impactmodifiers, the acid-modified polyolefin resin is preferred, and thepolyolefin resin may partly have a carbon-carbon double bond. The ratioof the impact modifier relative to 100 parts by weight of thesemicrystalline thermoplastic resin is, for example, about 1 to 30 partsby weight, preferably about 1 to 25 parts by weight, and more preferablyabout 5 to 20 parts by weight.

The resin particle (B) may further contain another thermoplastic resinor a conventional additive as other component (s). Examples of theconventional additive may include a stabilizer, a filler (a nonfibrousfiller), a coloring agent, a dispersing agent, a preservative, anantioxidant, and a defoaming agent. These other components may be usedalone or in combination. The total ratio of these other componentsrelative to 100 parts by weight of the semicrystalline thermoplasticresin may be, for example, not more than 10 parts by weight (e.g., about0.01 to 10 parts by weight).

(C) Matrix Resin

The matrix resin (C) is a resin component that is a matrix of acomposition containing the reinforcing fiber (A) [and the resin particle(B)], and can suitably be selected according to purposes or desiredcharacteristics.

Such a matrix resin (C) contains a resin (a resin component). The resin,which can be selected according to purposes or desired characteristicsor physical properties, may be a thermoplastic resin [for example, anacrylic resin, a polyolefin resin (e.g., a polypropylene), a polyamideresin (e.g., the above-exemplified polyamide resin), a polyester resin(e.g., an aromatic polyester resin such as a poly (ethyleneterephthalate)), a polycarbonate resin, a poly(phenylene ether) resin, apoly(phenylene sulfide) resin, a polysulfone resin, a polyetherketoneresin, a polyetheretherketone resin, a polyimide resin, and apolyetherimide resin] or a curable resin (a thermosetting orlight-curable resin). The resins may be used alone or in combination.

In particular, according to the present invention, the thermosettingresin can preferably be used, from the point of view of strength orthermal characteristics, in combination with the resin particle (B).Thus, the matrix resin may contain a thermosetting resin.

The thermosetting resin may include, for example, an epoxy resin, anunsaturated polyester resin, a vinyl ester resin, an acrylic resin, aphenolic resin, a urea resin, a melamine resin, an aniline resin, apolyimide resin, and a bismaleimide resin. These thermosetting resinsmay be used alone or in combination.

Among these thermosetting resins, in particular, the epoxy resin ispreferred. The epoxy resin may include, for example, a glycidylether-based epoxy resin, a glycidylamine-based epoxy resin (e.g.,tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol,triglycidylaminocresol, diglycidylaniline, andN,N-diglycidyl-4-glycidyloxyaniline), a glycidyl ester-based epoxy resin[for example, a diglycidyl ester of a dicarboxylic acid (e.g., anaromatic dicarboxylic acid or a hydrogenated product thereof, such asterephthalic acid, isophthalic acid, phthalic acid, tetrahydrophthalicacid, or hexahydrophthalic acid)], an alkene oxide (e.g.,vinylcyclohexene dioxide), and triglycidyl isocyanurate.

The glycidyl ether-based epoxy resin may include, for example, an epoxyresin (polyglycidyl ether) having an aromatic skeleton and an epoxyresin (polyglycidyl ether) having an aliphatic skeleton. Examples of theepoxy resin having an aromatic skeleton may include a bisphenol-basedepoxy resin [a reaction product of a bisphenol or an alkylene oxideadduct thereof and epichlorohydrin (such as a bisphenol A-based epoxyresin, a bisphenol F-based epoxy resin, a bisphenol S-based epoxy resin,or a brominated bisphenol-based epoxy resin)], a phenol-based epoxyresin (e.g., a phenol novolac epoxy resin, a cresol novolac epoxy resin,a naphthol novolac epoxy resin, a bisphenol A novolac epoxy resin, abisphenol F novolac epoxy resin, a biphenyl skeleton-containing phenolnovolac resin, and a xylylene skeleton-containing phenol novolac resin),a dicyclopentadiene-based epoxy resin, and a glycidyl ether having anaphthalene skeleton [for example, a di(glycidyloxy)naphthalene such as1,5-di(glycidyloxy)naphthalene, andbis[2,7-di(glycidyloxy)naphthyl]methane]. Examples of the epoxy resinhaving an aliphatic skeleton may include an alkanediol diglycidyl ether(e.g., a C₂₋₁₀alkanediol diglycidyl ether such as butanediol diglycidylether, neopentyl glycol diglycidyl ether, or 1,6-hexanediol diglycidylether), a polyalkanediol diglycidyl ether (e.g., a polyC₂₋₄alkanedioldiglycidyl ether such as polypropylene glycol diglycidyl ether), and adi- to hexa-glycidyl ether of an alkanetri- to hexa-ol (e.g., a di- ortri-glycidyl ether of a C₃₋₁₀alkanetri- or tetra-ol, such astrimethylolpropane di- or tri-glycidyl ether, or glycerin di- ortri-glycidyl ether).

For the alkylene oxide adduct of the bisphenol, the mole number ofalkylene oxides added to 1 mol of hydroxyl groups of the bisphenol maybe, for example, not less than 1 mol (e.g., about 1 to 20 mol),preferably about 1 to 15 mol, and more preferably about 1 to 10 mol.

These epoxy resins may be used alone or in combination. Among theseepoxy resins, the epoxy resin having an aromatic skeleton, for example,a bisphenol-based epoxy resin, is preferred in light of strength orother characteristics. Thus, the epoxy resin may comprise at least anepoxy resin having an aromatic skeleton or may comprise an epoxy resinhaving an aromatic skeleton and another epoxy resin (for example, anepoxy resin having an aliphatic skeleton) in combination.

The epoxy resin may further comprise a monofunctional epoxy compound (ora diluent) {for example, a monoglycidyl ether [e.g., an alkyl glycidylether (e.g., 2-ethylhexyl glycidyl ether), an alkenyl glycidyl ether(e.g., allyl glycidyl ether), an aryl glycidyl ether (e.g., phenylglycidyl ether)], and an alkene oxide (such as octylene oxide or styreneoxide)}. For combination of the epoxy resin and the monofunctional epoxycompound, the ratio of the epoxy resin relative to the monofunctionalepoxy compound [the former/the latter (weight ratio)] may be, forexample, about 99/1 to 50/50, preferably about 97/3 to 60/40, and morepreferably about 95/5 to 70/30.

The epoxy resin (or a composition containing the epoxy resin and themonofunctional epoxy compound) may be solid or liquid at a roomtemperature (e.g., about 20 to 30° C.). The liquid epoxy resin may havea viscosity (at 25° C.) of, for example, about 50 to 50000 mPa·s,preferably about 100 to 40000 mPa·s (e.g., about 200 to 35000 mPa·s),and more preferably about 300 to 30000 mPa·s (e.g., about 500 to 25000mPa·s) or may have a viscosity (at 25° C.) of not lower than 1000 mPa·s(e.g., about 2000 to 50000 mPa·s, preferably about 3000 to 30000 mPa·s,and more preferably about 5000 to 25000 mPa·s).

In a case where the resin comprises a thermosetting resin, the matrixresin may further contain a curing agent or a curing accelerator.Specifically, the matrix resin may comprise a resin (a thermosettingresin) and a curing agent or a curing accelerator for the resin.

The curing agent can suitably be selected according to the species ofthe resin. For example, in a case where the resin is an epoxy resin, thecuring agent may include, for example, an amine-based curing agent, aphenolic resin-based curing agent (e.g., a phenol novolac resin and acresol novolac resin), an acid anhydride-based curing agent [e.g., analiphatic dicarboxylic anhydride (such as dodecenylsuccinic anhydride),an alicyclic dicarboxylic anhydride (such as tetrahydrophthalicanhydride, methyltetrahydrophthalic anhydride, or hexahydrophthalicanhydride), and an aromatic dicarboxylic anhydride (such as phthalicanhydride, trimelliticanhydride, pyromelliticanhydride, orbenzophenonetetracarboxylic anhydride)], a polymercaptan-based curingagent, and a latent curing agent (such as boron trifluoride-aminecomplex, dicyandiamide, or a carbohydrazide).

The amine-based curing agent may include, for example, an aromaticamine-based curing agent, an aliphatic amine-based curing agent, analicyclic amine-based curing agent, and an imidazole compound or a saltthereof (e.g., a formate, a phenol salt, a phenol novolac salt, and acarbonate). Examples of the aromatic amine-based curing agent mayinclude a polyaminoarene (e.g., a diaminoarene such asp-phenylenediamine or m-phenylenediamine), a polyamino-alkylarene (e.g.,a diamino-alkylarene such as diethyltoluenediamine), apoly(aminoalkyl)arene [e.g., a di(aminoalkyl)arene such asxylylenediamine], a poly(aminoaryl)alkane [e.g., a di(aminoaryl)alkanesuch as diaminodiphenylmethane], a poly(amino-alkylaryl)alkane [e.g., adi(amino-alkylaryl)alkane such as4,4′-methylenebis(2-ethyl-6-methylaniline)], a bis(aminoarylalkyl)arene{e.g., 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene and1,4-bis[2-(4-aminophenyl)-2-propyl]benzene}, a di(aminoaryl) ether(e.g., diaminodiphenyl ether), a di(aminoaryloxy)arene [e.g.,1,3-bis(3-aminophenoxy)benzene], and a di(aminoaryl) sulfone (e.g.,diaminodiphenyl sulfone). Examples of the aliphatic amine-based curingagent may include ethylenediamine, hexamethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine, anddiethylaminopropylamine. Examples of the alicyclic amine-based curingagent may include menthenediamine, isophoronediamine,bis(4-amino-3-methylcyclohexyl)methane,3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5] undecane, andnorbornanediamine. Examples of the imidazole compound may include analkylimidazole such as 2-methylimidazole, 2-phenylimidazole,2-heptadecylimidazole, or 2-ethyl-4-methylimidazole; and anarylimidazole such as 2-phenylimidazole, 2-phenyl-4-methylimidazole,2-phenyl-4-methyl-5-hydroxymethylimidazole, or1-benzyl-2-phenylimidazole.

The curing agents may be used alone or in combination. The curing agentcan also act as a curing accelerator.

Among them, in particular, the amine-based curing agent (for example, anaromatic amine-based curing agent) may preferably be used.

The ratio of the curing agent can suitably be selected according to thespecies of the epoxy resin (e.g., epoxy equivalent), the species of thecuring agent, or others. For example, the ratio of the curing agentrelative to 100 parts by weight of the epoxy resin may be about 0.1 to300 parts by weight, preferably about 1 to 250 parts by weight, morepreferably about 3 to 200 parts by weight (e.g., about 4 to 150 parts byweight), and particularly about 5 to 100 parts by weight.

The curing accelerator can also suitably be selected according to thespecies of the resin. For example, in a case where the resin comprisesan epoxy resin, the curing accelerator may include, for example, aphosphine compound (e.g., ethylphosphine, propylphosphine,trialkylphosphine, phenylphosphine, and triphenylphosphine) and an aminecompound (e.g., a secondary to tertiary amine such as triethylamine,piperidine, benzyldimethylamine, triethanolamine, dimethylaminoethanol,triethylenediamine, tris(dimethylaminomethyl)phenol orN,N-dimethylpiperazine, or a salt thereof). The curing accelerators maybe used alone or in combination.

The ratio of the curing accelerator can suitably be selected accordingto the species of the curing agent, or others. For example, the ratio ofthe curing accelerator relative to 100 parts by weight of the epoxyresin may be about 0.01 to 100 parts by weight, preferably about 0.05 to50 parts by weight, and more preferably about 1 to 30 parts by weight.

In the composition (or the molded article described later) of thepresent invention, the proportion of the resin particle (B) in the totalamount of the resin particle (B) and the matrix resin (C) (when thematrix resin contains a curing agent and/or a curing accelerator, theamount of the matrix resin (C) means the total amount of the resin andthe curing agent and/or the curing accelerator) can be selected from arange of not more than 50% by weight (e.g., about 0.1 to 40% by weight)or may, for example, be not more than 30% by weight (e.g., about 0.5 to25% by weight), preferably not more than 20% by weight (e.g., about 1 to18% by weight), and more preferably not more than 15% by weight (e.g.,about 2 to 12% by weight) or may be not more than 10% by weight (e.g.,about 0.5 to 8% by weight, and preferably about 1 to 5% by weight).

In the composition (or the molded article described later) of thepresent invention, the proportion of the resin particle (B) in the totalamount of the resin particle (B) and the matrix resin (C) (when thematrix resin contains a curing agent and/or a curing accelerator, theamount of the matrix resin (C) means the total amount of the resin andthe curing agent and/or the curing accelerator) can be selected from arange of not more than 30% by volume (e.g., about 0.01 to 25% by volume)or may, for example, be not more than 20% by volume (e.g., about 0.1 to15% by volume), preferably not more than 10% by volume (e.g., about 0.3to 8% by volume), and more preferably not more than 5% by volume (e.g.,about 0.5 to 3% by volume).

According to the present invention, the reinforcing effect by thereinforcing fiber is sufficiently obtainable if the proportion of theresin particle (B) is low.

In the composition (or the molded article described later) of thepresent invention, the ratio of the total amount of the resin particle(B) and the matrix resin (C) relative to 100 parts by weight of thereinforcing fiber (A) may be, for example, about 1 to 70 parts byweight, preferably about 2 to 50 parts by weight, and more preferablyabout 3 to 30 parts by weight.

The composition of the present invention may optionally contain anyother component that does not damage the effects of the presentinvention. Such a component can suitably be selected as usage or others.For example, the component may include a stabilizer, a filler (anon-fibrous filler), a coloring agent, a dispersing agent, apreservative, an antioxidant, and a defoaming agent. These componentsmay be used alone or in combination.

The composition of the present invention may contain anelectroconductive particle or may usually be free from anelectroconductive particle.

(Form of Composition)

The form of the composition of the present invention comprises thereinforcing fiber (A), the resin particle (B), and the matrix resin (C)(and optionally other components, the same applies hereinafter). Thecomposition may usually be in the form that the reinforcing fiber (A) isimpregnated with a mixture containing the resin particle (B) and thematrix resin (C) (or the matrix resin (C) containing the resin particle(B)) [or in the form that the mixture is attached to the reinforcingfiber (A)]. Such a form can also be expressed as the form that thereinforcing fiber (A) and the resin particle (B) are dispersed in thematrix resin (C).

Such a composition may be a pre-preg (an intermediate material formolding). For example, in a case where the matrix resin (C) is athermosetting resin component [for example, an epoxy resin component(e.g., a composition containing an epoxy resin and a curing agent)], thecomposition may be in a semi-cured (or tack free) state.

The form of the composition can be selected according to the shape ofthe reinforcing fiber (A), or others. Concrete forms may include, forexample, (i) a form in which a plurality of the reinforcing fibers (A)arranged in the same direction (or one direction) is impregnated withthe mixture and (ii) a form in which a cloth formed with the reinforcingfiber (A) is impregnated with the mixture. A pre-preg composition havingthe form (i) is known as UD pre-preg or others. A pre-preg compositionhaving the form (ii) is known as cloth pre-preg or others.

(Process for Producing Composition)

Such a composition is obtainable through a resin particle productionstep and an impregnation step. In the resin particle production step,the semicrystalline thermoplastic resin and an aqueous mediumincompatible with the resin are melt-kneaded to prepare a melt-kneadedproduct, and the aqueous medium is removed from the melt-kneaded productwith a hydrophilic solvent to give the resin particle (B). In theimpregnation step, the reinforcing fiber (A) is impregnated with theresulting resin particle (B) and the matrix resin (C).

In the resin particle production step, the resin particle (B) isobtainable by a commonly-used forced emulsification in which the resinis melt-kneaded with the aqueous medium. According to the presentinvention, the resin is shaped into a particulate form by the forcedemulsification and then the shaped resin is prepared under a conditiondifferent from the conventional method (particularly, under a dryingtreatment at a low temperature) to give a semicrystalline resin particlehaving a specific degree of crystallinity. As the forced emulsification,there may be utilized a commonly-used method, for example, a methoddescribed in Japanese Patent Application Laid-Open Publication No.2010-132811.

The aqueous medium can be selected according to the species of thesemicrystalline thermoplastic resin and may include, for example, aheat-melting saccharide (e.g., an oligosaccharide such as sucrose ormaltotriose; and a sugar alcohol such as xylitol, erythritol, sorbitol,or mannitol) and a water-soluble polymer (e.g., a water-solublesynthetic polymer such as a poly(ethylene glycol), a poly(vinylalcohol), a poly(sodium acrylate), or a polyacrylamide; and apolysaccharide such as a starch or a methyl cellulose). These aqueousmedia may be used alone or in combination.

In a case where the semicrystalline thermoplastic resin is a polyamideresin (in particular, an alicyclic polyamide resin), the aqueous mediummay be a water-soluble polymer (for example, a water-soluble syntheticpolymer such as a poly(ethylene glycol) or a poly(vinyl alcohol)). Forexample, as the poly(ethylene glycol), “PEG-20000”, “PEG-11000”,“PEG-1000”, and “PEG-200”, each manufactured by NOF CORPORATION, may beused alone or in combination. The viscosity of the aqueous medium is onefactor for controlling a particle size of a resin particle which isobtained by the forced emulsification. The selection of the viscosityvaries according to a desired particle size, a species or molecularweight of the semicrystalline thermoplastic resin, a volume ratio of thesemicrystalline thermoplastic resin and the aqueous medium, a shear ratein compounding, or other conditions. The viscosity may be regulated bycombination of these conditions. From the viewpoint of easy regulationto an appropriate particle size, the aqueous medium may particularly bethe poly (ethylene glycol) (s).

The weight ratio of the aqueous medium relative to 100 parts by weightof the semicrystalline thermoplastic resin may be, for example, about 10to 100 parts by weight, preferably about 20 to 100 parts by weight, andmore preferably about 30 to 100 parts by weight. The volume ratio of theaqueous medium relative to the total volume of the aqueous medium andthe semicrystalline thermoplastic resin may be not less than 50% byvolume (for example, about 50 to 90% by volume). An excessively highratio of the aqueous medium may reduce productivity. In contrast, anexcessively low ratio of the aqueous medium may make production of aresin particle having a small particle size difficult.

The melt-kneading temperature is a temperature not lower than themelting point or softening point of the semicrystalline thermoplasticresin and can be selected according to the species of thesemicrystalline thermoplastic resin. For example, for an alicyclicpolyamide resin, the melt-kneading temperature is, e.g., not lower than250° C. (e.g., about 250 to 350° C.), preferably about 260 to 320° C.,and more preferably about 270 to 300° C.

The cooling method after melt-kneading is not particularly limited to aspecific one. From the viewpoint of productivity, in a case where thesemicrystalline thermoplastic resin is a polyamide resin (in particular,an alicyclic polyamide resin), forcible cooling (rapid cooling) ispreferred. For example, the cooling rate may be not less than 1° C./min.(e.g., about 1 to 10° C./min.). The cooling method exerts less influenceon the crystallinity of the resin particle compared with the dryingcondition (heating) after solidification. For a polyamide resin having alow crystallization rate (for example, an alicyclic polyamide resin),the resin may be forcibly cooled.

For the method of removing the aqueous medium from the kneaded productafter cooling, a hydrophilic solvent is used. Practically, the aqueousmedium is removed by washing the kneaded product with a hydrophilicsolvent. As the hydrophilic solvent, for example, there may preferablybe used water, an alcohol (e.g., a lower alcohol such as ethanol), awater-soluble ketone (e.g., acetone), or other solvents.

In the method of drying the resin particle obtained by removing theaqueous medium, the resin particle is preferably dried at a lowtemperature from the viewpoint of prevention of excessivecrystallization. The degree of crystallinity of the resin particlevaries according to the species of the resin and the aqueous medium, theprocess temperature, the cooling method, the drying method after removalof the aqueous medium, or other factors. The combination of thesefactors is diversified. Although it is difficult to simply define thecondition for obtaining a semicrystalline resin having a low degree ofcrystallinity, the drying method among these factors particularly exertsgreat influence on the crystallinity of the resin.

The drying temperature can be selected according to the species of thesemicrystalline thermoplastic resin. The drying temperature may be nothigher than (Tg+40)° C., for example, not higher than (Tg+30)° C.,preferably not higher than (Tg+20)° C., and more preferably not higherthan (Tg+10)° C., or may particularly be a temperature not higher thanthe glass transition temperature under a reduced pressure, where Tgrepresents the glass transition temperature of the semicrystallinethermoplastic resin. Specifically, for example, in a case where thesemicrystalline thermoplastic resin is an alicyclic polyamide resin, thedrying temperature may be not higher than the glass transitiontemperature, for example, may be about (Tg−50)° C. to Tg° C. andpreferably about (Tg−30)° C. to (Tg−10)° C. Moreover, in a case wherethe semicrystalline thermoplastic resin is an aliphatic polyamide resin,the drying temperature may be not higher than the glass transitiontemperature, for example, may be about Tg° C. to (Tg+40)° C. andpreferably about (Tg+10)° C. to (Tg+35)° C.

In the impregnation step, the reinforcing fiber (A), the resin particle(B), and the matrix resin (C) are mixed to give an impregnationcomposition. Practically, the reinforcing fiber (A) is impregnated with(or attached to) a mixture containing the resin particle (B) and thematrix resin (C) to give an impregnation composition.

Concrete impregnation methods may include (a) a method of impregnatingthe reinforcing fiber (A) with the mixture that is liquid, (b) a methodof contacting a sheet formed of the mixture with the reinforcing fiber(A) under an applied pressure, and other methods.

In the method (a), the liquid mixture to be used may be the matrix resin(C) that is liquid (liquid at the ordinary temperature) or may beprepared by a proper solvent (a poor solvent to the resin particle (B)).Moreover, the liquid mixture can also be obtained by melting the matrixresin (C).

[Molded Article]

The present invention also includes a molded article of the composition(a molded article comprising the composition). The molded article, whichcontains the reinforcing fiber (A) and the matrix resin (C) in which thereinforcing fiber (A) is dispersed, can be referred to as a composite [afiber-reinforced composite (in particular, a carbon fiber composite)].

The process for producing (molding) the molded article can be selectedaccording to the form of the composition or the species of the componentof the composition, or others. For example, in a case where the matrixresin (C) is a thermosetting resin component, the molded article can beproduced by curing the composition (specifically, the composition havinga desired shape). That is, the molded article, in which the matrix resin(C) is a thermosetting resin component, can be referred to as a curedproduct of the composition. The molding process can also be selectedaccording to the degree of curing of the thermosetting resin component(e.g., non-curing or semi-curing), or others. The molded article mayhave a one-dimensional form (such as a rod form), a two-dimensional form(such as a sheet form), or a three-dimensional form.

Concrete molding processes may include a hand lay up molding, a SMC(sheet molding compound) press molding, a RIMP (resin infusion moldingprocess), a pre-preg press molding, a pre-preg autoclave, a winding(such as a filament winding or a pin winding), a pultrusion molding, aBMC (bulk molding compound) molding, or other processes.

As described above, the molded article is obtainable. According to themolded article (or composition) of the present invention, the resinparticle (B) can increase the reinforcing function of the reinforcingfiber (A) (for example, interlaminar toughness). In particular,according to the present invention, the resin particle (B) having aspecific form and a specific particle size efficiently improves thereinforcing effect by the reinforcing fiber (A), and a sufficientreinforcing function is achievable at a relatively low proportion of theresin particle (B).

EXAMPLES

The following examples are intended to describe this invention infurther detail and should by no means be interpreted as defining thescope of the invention. Abbreviations of materials used in Examples andComparative Examples are shown below. Resin particles and test piecesobtained in Examples and Comparative Examples were evaluated for thefollowing items.

[Materials]

Alicyclic PA: alicyclic polyamide, “TROGAMID CX7323” manufactured byDaicel-Evonik Ltd., melting point: 247° C.

Alicyclic PA particle: polyamide 12 particle obtained by chemicalpulverization shown below (dissolution in a solvent and thenre-precipitation for powdering)

In a 1000-mL pressure glass autoclave, 18 g of an alicyclic polyamide(“TROGAMID CX7323” manufactured by Daicel-Evonik Ltd.), 32 g of apoly(vinyl alcohol) (“GOHSENOL GM-14” manufactured by The NipponSynthetic Chemical Industry Co., Ltd.), 300 g of N-methyl-2-pyrrolidoneas an organic solvent were put, and 99% by volume or more of anatmospheric gas in the autoclave was replaced with nitrogen gas. Then,the contents of the autoclave were heated to 180° C. and were stirredfor 4 hours until the polymer was dissolved. Thereafter, 350 g ofion-exchange water as a poor solvent was added dropwise to the autoclaveat a speed of 3 g/min. through a liquid transfer pump. At the time whenabout 200 g of ion-exchange water was added, the liquid system in theautoclave turned white. After the addition of the whole amount ofion-exchange water was completed, the temperature was lowered whilestirring. The resulting suspension was filtered to give a precipitatewhich was then subjected to slurry washing by adding 700 g ofion-exchange water. The washed product was filtered to give aprecipitate which was then vacuum-dried at 80° C. for 10 hours to giveabout 17 g of a white solid.

PA12: polyamide 12, “VESTAMID L1600” manufactured by Daicel-Evonik Ltd.

PA12 particle: polyamide 12 particle obtained by chemical pulverization,“VESTOSINT 2158” manufactured by Daicel-Evonik Ltd.

PA1010: polyamide 1010, “VESTAMID Terra BS1393” manufactured byDaicel-Evonik Ltd.

Amorphous PA: aromatic polyamide, “TROGAMID T5000” manufactured byDaicel-Evonik Ltd.

Matrix resin: mixture of epoxy resin (“jER828” manufactured byMitsubishi Chemical Corporation) and amine-based curing agent (“jERCUREW” manufactured by Mitsubishi Chemical Corporation)

Carbon fiber: “TC-33” manufactured by HONLU TECHNOLOGY CO., LTD.,average fiber diameter: about 7 μm

[Average Particle Size]

A resulting resin particle was dispersed in water, and the averageparticle size thereof was measured by a laser diffraction/scatteringparticle diameter distribution measuring apparatus (“LA920” manufacturedby Horiba, Ltd.).

[Crystallization Peak (DSC)]

A resulting resin particle was heated from a room temperature to 300° C.at 10° C./min. by using a differential scanning calorimeter (“X-DSC7000”manufactured by Seiko Instruments Inc.), and the presence or absence ofa crystallization peak between these temperatures (between the glasstransition temperature and the melting point) was observed.

[Wide-Angle X-Ray Diffraction (WAXD)]

The following measurement was performed using an intelligent X-raydiffraction system (“SmartLab” manufactured by Rigaku Corporation). Aresulting resin particle was placed on a center of a horizontalround-table sample stage, and a package measurement program “Generalpurpose (focusing method)” was executed to give an X-ray diffractionpattern under the following measurement conditions by focusing method.

(Measurement Conditions)

Primary X-ray source: rotating anticathode X-ray generator having Cu asan anticathode (acceleration voltage−electric current: 45 kV−200 mA)

Scanning step: 0.02°

Scanning rate: 4°/min.(2θ)

[Degree of Crystallinity]

An X-ray powder diffraction software (“PDXL Ver2.3.1.0” manufactured byRigaku Corporation) was used for fitting (method: FP method, peak shape:logarithmic normal distribution, background precision: none) to adiffraction curve obtained by the wide-angle X-ray diffraction, therebyseparating a crystal diffraction peak and an amorphous halo. The degreeof crystallinity (%) was determined from the following equation.

Degree of crystallinity=[Sum of integrated intensity of crystaldiffraction peak (cps·deg)]/[Sum of integrated intensity of crystaldiffraction peak and amorphous halo (cps·deg)]×100%

[Interlaminar Fracture Toughness Test]

For a test piece A obtained, a mode I interlaminar fracture toughnessvalue (G_(IC)) at initial crack growth was measured in accordance withJapanese Industrial Standards (JIS) K7086-1993.

[Notched Charpy Impact Strength]

For a test piece B obtained, a Charpy impact strength was measured at atest temperature of 23° C. in accordance with IS0179/1eA.

Example 1

(Production of Resin Particle)

The alicyclic PA was shaped into a fine particulate form by forcedemulsification using a poly (ethylene glycol) in accordance withExamples of Japanese Patent Application Laid-Open Publication No.2010-132811. A melt-kneaded product containing an alicyclic PS and apoly(ethylene glycol) extruded from a die of an extruder was forciblycooled by a spot cooler and then washed with water for removal of onlythe poly (ethylene glycol). The washed product was dried at atemperature of 120° C. for 24 hours under a reduced pressure to give aresin particle (powder). The resin particle had an average particle sizeof 21 μm and had a crystallization peak observed under a heatingcondition of 10° C./min. by DSC. The DSC chart (sound-absorbing curve)is shown in FIG. 1. As apparent from FIG. 1, a high peak bycrystallization is observed around 170° C., and the degree ofcrystallinity is also low. The results show that the obtained particlehas a low crystallinity.

(Production of Test Piece A)

The resin particle was added in a ratio of 5% by weight to the matrixresin, and the resulting mixture was stirred using a hot stirrer for 24hours under conditions of 100° C. and 600 rpm. Then, the mixture wasallowed to stand in a vacuum vessel for one hour for defoaming to give amatrix resin containing the resin particle.

By hand lay up method, a woven fabric (plain weave) of the carbon fiberwas impregnated with the resulting matrix resin containing the resinparticle, and then another woven fabric of the carbon fiber waslaminated on the woven fabric, and the laminate was impregnated with thematrix resin. This procedure was repeated, and a 12-layer laminate wasobtained.

Two types of laminates were produced with respect to each proportion.Specifically, one type was a 12-layer laminate having 12 woven fabrics,and the other was a 13-layer laminate having 12 woven fabrics and onepolyimide film (“KAPTON” manufactured by DU PONT-TORAY CO., LTD.) [the13-layer laminate in which the polyimide film having a thickness of 25μm was laminated for precrack formation after lamination of the 6thwoven fabric].

Each laminate was put in a thermostatic bath in a state that a pressureof about 8 MPa was loaded, and was allowed to stand at 100° C. for 2hours and then at 175° C. for 4 hours for curing treatment. Theresulting cured product had a thickness of about 2.8 mm. For thelaminate containing the polyimide film, the polyimide film was pulledout from the laminate after curing treatment. Thereafter, each laminatewas cut into 140 mm long, 25 mm wide, and 2.8 mm thick.

(Production of Test Piece B)

The resin particle was added in a ratio of 20% by weight to the matrixresin, and the mixture was formed into a shape in accordance withISO179/1eA to give a test piece B.

Comparative Example 1

A test piece was produced in the same manner as Example 1 except thatthe alicyclic PA particle obtained by chemical pulverization was used asthe resin particle. The resin particle had an average particle size of23 μm and had no crystallization peak observed under a heating conditionof 10° C./min. by DSC. The DSC chart (sound-absorbing curve) is shown inFIG. 2. As apparent from FIG. 2, no peak by crystallization is observedaround 170° C., and this shows that the obtained particle has a highcrystallinity.

FIG. 3 is a wide-angle X-ray diffraction chart of alicyclic polyamideparticles obtained in Example 1 and Comparative Example 1. As apparentfrom FIG. 3, the X-ray spectrum of the alicyclic polyamide particleobtained in Example 1 has a gentle mountain shape, which shows that thealicyclic polyamide particle has a low crystallinity and unidentifiablecrystal form; in contrast, the X-ray spectrum of the alicyclic polyamideparticle obtained in Comparative Example 1 has two sharp peaks at 2θ of17.3° and 2θ of 19.7°, which shows that the alicyclic polyamide particlehas an α-type crystal structure and a high degree of crystallinity, andthus the alicyclic polyamide particle has a high crystallinity.

Comparative Example 2

A test piece was produced in the same manner as Example 1 except for thefollowing: in the production of the resin particle, the melt-kneadedproduct was allowed to cool without using the spot cooler, and afterremoval of the poly(ethylene glycol) the resulting product was dried byheating at 180° C. for 3 hours without drying under a reduced pressure.The resin particle had an average particle size of 23 μm and had nocrystallization peak observed under a heating condition of 10° C./min.by DSC, and thus the resin particle had a high degree of crystallinity.

Example 2

A test piece was produced in the same manner as Example 1 except for thefollowing: in the production of the resin particle, the PA12 and asaccharide were used instead of the alicyclic PA and the poly(ethyleneglycol), the melt-kneaded product was allowed to cool without using thespot cooler, and after removal of the saccharide the resulting productwas dried by heating at 80° C. for 3 hours without drying under areduced pressure. The resin particle had an average particle size of 20μm and had a crystallization peak observed under a heating condition of10° C./min. by DSC. The DSC chart (sound-absorbing curve) is shown inFIG. 4. As apparent from FIG. 4, a peak by crystallization is observedaround 170° C. FIG. 5 is a wide-angle X-ray diffraction chart. Asapparent from FIG. 5, the X-ray spectrum of the obtained PA12 particlehas one peak at 20 of 21.5°, which shows that the PA12 particle has aγ-type crystal structure.

Comparative Example 3

A test piece was produced in the same manner as Example 1 except thatthe PA12 particle obtained by chemical pulverization was used as theresin particle. The resin particle had an average particle size of 24 μmand had no crystallization peak observed under a heating condition of10° C./min. by DSC. The DSC chart (sound-absorbing curve) is shown inFIG. 6. As apparent from FIG. 6, no peak by crystallization is observedaround 170° C. FIG. 7 is a wide-angle X-ray diffraction chart. Asapparent from FIG. 7, the X-ray spectrum of the PA12 particle obtainedin Comparative Example 3 has two peaks at 20 of 20.6° and 20 of 22.3°,which shows that the PA12 particle has an α-type crystal structure.

Example 3

A test piece was produced in the same manner as Example 1 except for thefollowing: in the production of the resin particle, the PA1010 and asaccharide were used instead of the alicyclic PA and the poly(ethyleneglycol), the melt-kneaded product was allowed to cool without using thespot cooler, and after removal of the saccharide the resulting productwas dried by heating at 80° C. for 3 hours without drying under areduced pressure. The resin particle had an average particle size of 22μm and had a crystallization peak observed under a heating condition of10° C./min. by DSC. FIG. 8 is a wide-angle X-ray diffraction chart. Asapparent from FIG. 8, the X-ray spectrum of the PA1010 particle obtainedin Example 3 has two peaks at 28 of 20.4° and 28 of 23.6°, which showsthat the PA1010 particle has an α-type crystal structure.

Comparative Example 4

The PA1010 was shaped into a fine particulate form by chemicalpulverization. The resulting fine particle was used to prepare a testpiece in the same manner as Example 1. The resin particle had an averageparticle size of 18 μm and had no crystallization peak observed under aheating condition of 10° C./min. by DSC. FIG. 9 is a wide-angle X-raydiffraction chart. As apparent from FIG. 9, the X-ray spectrum of thePA1010 particle obtained in Comparative Example 4 has two peaks at 28 of20.0° and 28 of 24.1°, which shows that the PA1010 particle has anα-type crystal structure. The PA1010 particle had a degree ofcrystallinity higher than that of the PA1010 particle obtained inExample 3.

Example 4

A test piece was produced in the same manner as Example 1 except that,in the production of the resin particle, a poly(vinyl alcohol) was usedinstead of the poly(ethylene glycol). The resin particle had an averageparticle size of 11 μm and had a crystallization peak observed under aheating condition of 10° C./min. by DSC.

Example 5

A test piece was produced in the same manner as Example 1 except for thefollowing: in the production of the resin particle, the PA12 and asaccharide were used instead of the alicyclic PA and the poly(ethyleneglycol), the melt-kneaded product was allowed to cool without using thespot cooler, and after removal of the saccharide the resulting productwas dried by heating at 80° C. for 3 hours without drying under areduced pressure. The resin particle had an average particle size of 5μm and had a crystallization peak observed under a heating condition of10° C./min. by DSC.

Comparative Example 5

A test piece was produced in the same manner as Example 1 except for thefollowing: in the production of the resin particle, the amorphous PA wasused instead of the alicyclic PA, and after removal of the poly(ethyleneglycol) the resulting product was dried at 140° C. for 24 hours under areduced pressure. The resin particle had an average particle size of 19μm and had no crystallization peak observed under a heating condition of10° C./min. by DSC.

Comparative Example 6

A test piece was produced with no resin particle. Table 1 showsevaluation results of the resin particles and test pieces obtained inExamples and Comparative Examples.

TABLE 1 Compar- Compar- Compar- Compar- Compar- Compar- Exam- ativeative Exam- ative Exam- ative Exam- Exam- ative ative ple 1 Example 1Example 2 ple 2 Example 3 ple 3 Example 4 ple 4 ple 5 Example 5 Example6 Material Alicyclic PA12 PA1010 Alicyclic PA12 Amorphous — PA PA PA Tgabout about about about about about — 135° C. 50° C. 50° C. 135° C. 50°C. 150° C. Drying 120° C. 80° C. 180° C. 80° C. — 80° C. — 120° C. 80°C. 140° C. — temperature Crystal form — α-type α-type γ-type α-typeα-type α-type α-type γ-type — — Degree of 11% 71% 64% 70% 55% 41% 86%14% 73% — — crystallinity Average 21 μm 23 μm 23 μm 20 μm 24 μm 22 μm 18μm 11 μm 5 μm 19 μm — particle size Presence or Presence Absence AbsencePresence Absence Presence Absence Presence Presence — — absence of(Amorphous) peak by DSC G_(IC) 0.55 0.44 0.49 0.51 0.47 0.53 0.48 0.530.50 0.48 0.42 [kJ/m²] Impact strength 43 20 23 39 19 41 22 33 31 22 21[kJ/m²]

As apparent from the results shown in Table 1, in Examples the resinparticles have a crystallization peak and the test pieces have a highinterlaminar toughness and a high impact strength; in contrast, inComparative Examples the resin particles have no crystallization peakand the test pieces have a low interlaminar toughness.

INDUSTRIAL APPLICABILITY

The resin composition of the present invention is usable as acomposition for a fiber-reinforced composite. Such a composite isapplicable for structural members (structural materials) in variousfields, for example, vehicles (for example, aircraft, helicopters,rockets, automobiles, motorcycles, bicycles, trains, ships, andwheelchairs), artificial satellites, windmills, sports products (shaftsof golf clubs, tennis rackets), chassis (such as chassis of laptops),molded articles in medical fields (such as artificial bones), IC trays,fishing rods, and bridge piers.

1. A resin composition comprising (A) a reinforcing fiber, (B) a resinparticle, and (C) a matrix resin, wherein the reinforcing fiber (A)contains a carbon fiber, and the resin particle (B) contains asemicrystalline thermoplastic resin, the semicrystalline thermoplasticresin in the resin particle (B) has an exothermic peak in a temperaturerange between a glass transition temperature of the semicrystallinethermoplastic resin and a melting point of the semicrystallinethermoplastic resin, the exothermic peak being determined by heating theresin particle (B) at a rate of 10° C./min. by differential scanningcalorimetry (DSC), and the resin particle (B) has an average particlesize of 3 to 40 μm.
 2. The resin composition according to claim 1,wherein the semicrystalline thermoplastic resin is a polyamide resinhaving a melting point of not lower than 150° C.
 3. The resincomposition according to claim 2, wherein the polyamide resin has analicycilc structure and a glass transition temperature of not lower than100° C.
 4. The resin composition according to claim 1, wherein thesemicrystalline thermoplastic resin is a polyamide resin having a γ-typecrystal structure or a degree of crystallinity of not more than 50%. 5.The resin composition according to claim 4, wherein the polyamide resinis an aliphatic polyamide resin.
 6. The resin composition according toclaim 1, wherein the resin particle (B) further comprises an impactmodifier.
 7. The resin composition according to claim 1, wherein thematrix resin (C) is a thermosetting resin.
 8. The resin compositionaccording to claim 1, wherein the resin particle (B) has a sphericalshape and an average particle size of 15 to 25 μm.
 9. A process forproducing a resin composition recited in claim 1, the processcomprising: a resin particle production step comprising: melt-kneading asemicrystalline thermoplastic resin and an aqueous medium incompatiblewith the resin to prepare a melt-kneaded product, and removing theaqueous medium from the melt-kneaded product with a hydrophilic solventto give (B) a resin particle, and an impregnation step for impregnating(A) a reinforcing fiber with the resulting resin particle (B) and (C) amatrix resin.
 10. The process according to claim 9, wherein, in theresin particle production step, after the aqueous medium is removed, theresulting product is dried at a temperature of not higher than (Tg+40)°C., wherein Tg represents a glass transition temperature of thesemicrystalline thermoplastic resin.
 11. A molded article comprising aresin composition recited in claim
 1. 12. An additive for a compositioncomprising (A) a reinforcing fiber containing a carbon fiber and (C) amatrix resin to increase or improve a reinforcing effect of thereinforcing fiber (A), wherein the additive comprises (B) a resinparticle, the resin particle (B) contains a semicrystallinethermoplastic resin, the semicrysatlline thermoplastic resin in theresin particle (B) has an exothermic peak in a temperature range betweena glass transition temperature of the semicrystalline thermoplasticresin and a melting point of the semicrystalline thermoplastic resin,the exothermic peak being determined by heating the resin particle (B)at a rate of 10° C./min. by differential scanning calorimetry (DSC), andthe resin particle (B) has an average particle size of 3 to 40 μm.